Hubiera ido al parque si no hubiera llovido. Me hubiera gustado haber ido al parque ayer, pero tenía que trabajar. Iría al cine si tuviera tiempo de ir. Lo conocía desde hace 3 años antes de que tuviera su accidente.

I would have gone to the park had it not rained. Hubiera ido al parque de no haber llovido/si no hubiera llovido. I would have liked to have gone to the park yesterday but I had to work. Me hubiera gustado haber ido al parque ayer, pero tenía que trabajar. I would go to the movies if I had the time to go. Iría al cine si tuviera tiempo. I had known him for 3 years before he had his accident. Lo había conocido desde (hacía)[not necessary] tres años antes de que tuviera el accidente.

Thank all of you for helping me out with this. These types of conjugations drive me nuts!!

a)Hubiera ido al parque si no hubiera llovido. or Habría ido al parque sino hubiera llovido B) Sino hubiera llovido, hubiera ido al parque. 2. a) Me hubiese gustado haber ido al parque ayer pero tenía trabajo. 3. Iré al cine si tengo tiempo 4. Lo conocía de hace tres años antes cuando tuvo el accidente. Using hubiera/habria with conditionals boths of them are correct!! But the use of them change at the time of using facts or real situations. Take as example the first sentence. I would have gone (that is something hypotetical did not happen so in this case you can use both Habria/hubiese ido, but for the second part of the sentence Had it not rained (something that really happened or not) the only right answer is hubiera. You cannot say habria llovido. From the previous answer that you were given, I would not recomend to use is Daniel's last sentence "lo habia conocido". Lo conocía de hacía 3 años perhaps is a little more natural speaking.

Oh oh, your answer is different from Desiree's... Who's answer is correct?